The invention relates to apparatus for producing a bead on the periphery of a hollow cylinder. In this respect, the production of a bead must be understood in its general sense comprising also the production of a constriction (with or without a flange) or of a flange at the end of a hollow cylinder. Commonly assigned U.S. application Ser. No. 925,296, filed July 17, 1978, now U.S. Pat. No. 4,176,536 titled "Device For Producing A Bead On The Circumference Of A Hollow Cylinder", relates to this type of apparatus; the contents of said application being incorporated herein by reference thereto or an aid to understanding the present invention.
In the case of previously contemplated apparatus of this type (DOS No. 28 05 321), the inner tool is constructed functionally in one piece, while the outer tool consists of an outer ring and a depressor which is axially adjacent and radially adjustable in respect of the outer ring. This means that in the case of the known devices, during progressive production of the bead, the area of the hollow cylinder in which the bead is to be made is unsupported and is pressed inwardly by the tool while the area of the hollow cylinder adjacent the area in which the bead is to be made remains without adequate support from the outer tool and can in consequence become outwardly buckled. These two circumstances can individually, but in particular jointly, lead to undesired deformations of the hollow cylinder, particularly (wrinkling) creasing and buckling (bulging). Creasing in the area of the bead occurs for example if there is not adequate support from the inner tool, on the basis of impurities in the surface of the hollow cylinder, while outward buckling is caused by inadequate supporting from the depressor which, by virtue of its diameter being invariable and enlarged in relation to the hollow cylinder, only partially engages the hollow cylinder periphery.
An object of the invention is to eliminate the risk of such undesired deformation occurring and thereby achieve an improvement in quality of beaded hollow cylinders.
In particularly preferred embodiments, the above-noted problems are avoided by providing a depressor formed as a basket with springing tongues separated by axial slots and acted on by a tapered cylinder, so that the effective diameter of the depressor can be varied to optimize backing of the hollow cylinder during beading operation, while also permitting return of the basket to an enlarged diameter to accommodate placement and removal of the hollow cylinders being beaded. The advantageous effect of this solution is based thereby on the fact that, during the progressive production of the bead, the inner ring supports from inside the area on which the bead is to be provided, while the depressor with the cylinder liner and the basket with the spring-action tongues supports the entire hollow cylinder from outside, particularly also in the region adjacent to that in which the bead is to be made and stabilizes its circular shape. Hereby, the necessary radial adjustments of the depressor in relation to the outer ring and of the inner ring in relation to the carrier mandrel, necessary according to this purpose are derived directly from the apparatus drive through corresponding positioning means.
With regard to the construction of the cylinder liner and of the basket with spring tongues separated by axial slots, use is made of the per se known principle of screw clamp guides (DAS No. 23 35 745).
A relatively simple construction of the apparatus arises if the said radial adjustments are only indirectly derived from the drive of the apparatus. According to particularly preferred embodiments, this can be achieved if radially acting springs urge the inner ring and the carrier mandrel on the one hand and the outer ring and the depressor on the other into mutually coaxial positions. If the radial spacing of the outer ring from the axis of the carrier mandrel diminishes during progressive production of the bead, then under pressure of the outer ring which acts radially from outside, the inner ring is moved radially inwardly in relation to the carrier mandrel while under the radially acting pressure of the carrier mandrel from within, the depressor moves radially outwardly in relation to the outer ring.
In the case of a development of the apparatus according to the invention in which the outer tool is radially inwardly adjustable in relation to the inner tool against the force of a radially outwardly acting spring, as is known per se (German Pat. No. 750 476), and in which, therefore, from the drive of the apparatus, only a radially inwardly directed movement of the outer tool in relation to the inner tool is directly derived, another embodiment acquires a particularly simple and compact construction. This embodiment is characterized in that the springs acting on the outer tool, the cylinder liner and the inner ring are axially disposed and in that their forces are diverted in a radial direction via pairings of bevel ring faces.
The described radial adjustments can also be brought about against the forces of correspondingly disposed cylinder-piston units, a particularly simple and compact construction being achieved if the cylinder-piston units are axially disposed and if the forces are diverted in a radial direction through pairs of bevel rings enclosing the shaft of the carrier mandrel.
The apparatus according to the invention, both in per se known single arrangement (German Pat. No. 750 476) as well as in per se known multiple arrangement (DOS No. 22 18 396), is available for use with a plurality of inner and outer tools disposed in stellate fashion on a rotatingly drivable tool carrier. In the case of a multiple arrangement, it is expedient according to the invention for the controlled radial adjustability of the outer tools in relation to the inner tools to be by means of a control cam which engages partially around the tool carrier, and to be derived from the drive for the rotatable mandrels.